Backplanes for electro-optic displays

ABSTRACT

A backplane for an electro-optic display that includes a data line, a transistor, a pixel electrode connected to the data line via the transistor, the pixel electrode positioned adjacent to part of the data line so as to create a data line/pixel electrode capacitance. The backplane further including a shield electrode disposed adjacent to at least part of the data line so as to reduce the data line/pixel electrode capacitance.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/343,551, filed May 31, 2016, which is incorporated herein byreference in its entirety.

SUBJECT OF THE INVENTION

This invention relates to electro-optic display apparatuses, moreparticularly, to display backplanes that include thin-film transistorarrays.

BACKGROUND OF INVENTION

The present invention relates to backplanes for electro-optic displays.More specifically, it is related to display pixel designs where pixelelectrode crosstalk may be effectively reduced.

The term “electro-optic” as applied to a material or a display, is usedherein in its conventional meaning in the imaging art to refer to amaterial having first and second display states differing in at leastone optical property, the material being changed from its first to itssecond display state by application of an electric field to thematerial. Although the optical property is typically color perceptibleto the human eye, it may be another optical property, such as opticaltransmission, reflectance, luminescence or, in the case of displaysintended for machine reading, pseudo-color in the sense of a change inreflectance of electromagnetic wavelengths outside the visible range.

The term “gray state” is used herein in its conventional meaning in theimaging art to refer to a state intermediate two extreme optical statesof a pixel, and does not necessarily imply a black-white transitionbetween these two extreme states. For example, several of the E Inkpatents and published applications referred to below describeelectrophoretic displays in which the extreme states are white and deepblue, so that an intermediate “gray state” would actually be pale blue.Indeed, as already mentioned, the change in optical state may not be acolor change at all. The terms “black” and “white” may be usedhereinafter to refer to the two extreme optical states of a display, andshould be understood as normally including extreme optical states whichare not strictly black and white, for example the aforementioned whiteand dark blue states. The term “monochrome” may be used hereinafter todenote a drive scheme which only drives pixels to their two extremeoptical states with no intervening gray states.

The terms “bistable” and “bistability” are used herein in theirconventional meaning in the art to refer to displays comprising displayelements having first and second display states differing in at leastone optical property, and such that after any given element has beendriven, by means of an addressing pulse of finite duration, to assumeeither its first or second display state, after the addressing pulse hasterminated, that state will persist for at least several times, forexample at least four times, the minimum duration of the addressingpulse required to change the state of the display element. It is shownin published US Patent Application No. 2002/0180687 (see also thecorresponding International Application Publication No. WO 02/079869)that some particle-based electrophoretic displays capable of gray scaleare stable not only in their extreme black and white states but also intheir intermediate gray states, and the same is true of some other typesof electro-optic displays. This type of display is properly called“multi-stable” rather than bistable, although for convenience the term“bistable” may be used herein to cover both bistable and multi-stabledisplays.

The term “impulse” is used herein in its conventional meaning of theintegral of voltage with respect to time. However, some bistableelectro-optic media act as charge transducers, and with such media analternative definition of impulse, namely the integral of current overtime (which is equal to the total charge applied) may be used. Theappropriate definition of impulse should be used, depending on whetherthe medium acts as a voltage-time impulse transducer or a charge impulsetransducer.

Numerous patents and applications assigned to or in the names of theMassachusetts Institute of Technology (MIT) and E Ink Corporation haverecently been published describing encapsulated electrophoretic media.Such encapsulated media comprise numerous small capsules, each of whichitself comprises an internal phase containing electrophoretically-mobileparticles suspended in a liquid suspension medium, and a capsule wallsurrounding the internal phase. Typically, the capsules are themselvesheld within a polymeric binder to form a coherent layer positionedbetween two electrodes. The technologies described in these patents andapplications include:

-   -   (a) Electrophoretic particles, fluids and fluid additives; see        for example U.S. Pat. Nos. 7,002,728 and 7,679,814;    -   (b) Capsules, binders and encapsulation processes; see for        example U.S. Pat. Nos. 6,922,276 and 7,411,719;    -   (c) Films and sub-assemblies containing electro-optic materials;        see for example U.S. Pat. Nos. 6,982,178 and 7,839,564;    -   (d) Backplanes, adhesive layers and other auxiliary layers and        methods used in displays; see for example U.S. Pat. Nos.        D485,294; 6,124,851; 6,130,773; 6,177,921; 6,232,950; 6,252,564;        6,312,304; 6,312,971; 6,376,828; 6,392,786; 6,413,790;        6,422,687; 6,445,374; 6,480,182; 6,498,114; 6,506,438;        6,518,949; 6,521,489; 6,535,197; 6,545,291; 6,639,578;        6,657,772; 6,664,944; 6,680,725; 6,683,333; 6,724,519;        6,750,473; 6,816,147; 6,819,471; 6,825,068; 6,831,769;        6,842,167; 6,842,279; 6,842,657; 6,865,010; 6,967,640;        6,980,196; 7,012,735; 7,030,412; 7,075,703; 7,106,296;        7,110,163; 7,116,318; 7,148,128; 7,167,155; 7,173,752;        7,176,880; 7,190,008; 7,206,119; 7,223,672; 7,230,751;        7,256,766; 7,259,744; 7,280,094; 7,327,511; 7,349,148;        7,352,353; 7,365,394; 7,365,733; 7,382,363; 7,388,572;        7,442,587; 7,492,497; 7,535,624; 7,551,346; 7,554,712;        7,583,427; 7,598,173; 7,605,799; 7,636,191; 7,649,674;        7,667,886; 7,672,040; 7,688,497; 7,733,335; 7,785,988;        7,843,626; 7,859,637; 7,893,435; 7,898,717; 7,957,053;        7,986,450; 8,009,344; 8,027,081; 8,049,947; 8,077,141;        8,089,453; 8,208,193; 8,373,211; 8,389,381; 8,498,042;        8,610,988; 8,728,266; 8,754,859; 8,830,560; 8,891,155;        8,969,886; 9,152,003; and 9,152,004; and U.S. Patent        Applications Publication Nos. 2002/0060321; 2004/0105036;        2005/0122306; 2005/0122563; 2007/0052757; 2007/0097489;        2007/0109219; 2009/0122389; 2009/0315044; 2011/0026101;        2011/0140744; 2011/0187683; 2011/0187689; 2011/0292319;        2013/0278900; 2014/0078024; 2014/0139501; 2014/0300837;        2015/0171112; 2015/0205178; 2015/0226986; 2015/0227018;        2015/0228666; and 2015/0261057; and International Application        Publication No. WO 00/38000; European Patents Nos. 1,099,207 B1        and 1,145,072 B1;    -   (e) Color formation and color adjustment; see for example U.S.        Pat. Nos. 7,075,502 and 7,839,564;    -   (f) Methods for driving displays; see for example U.S. Pat. Nos.        5,930,026; 6,445,489; 6,504,524; 6,512,354; 6,531,997;        6,753,999; 6,825,970; 6,900,851; 6,995,550; 7,012,600;        7,023,420; 7,034,783; 7,116,466; 7,119,772; 7,193,625;        7,202,847; 7,259,744; 7,304,787; 7,312,794; 7,327,511;        7,453,445; 7,492,339; 7,528,822; 7,545,358; 7,583,251;        7,602,374; 7,612,760; 7,679,599; 7,688,297; 7,729,039;        7,733,311; 7,733,335; 7,787,169; 7,952,557; 7,956,841;        7,999,787; 8,077,141; 8,125,501; 8,139,050; 8,174,490;        8,289,250; 8,300,006; 8,305,341; 8,314,784; 8,373,649;        8,384,658; 8,558,783; 8,558,785; 8,593,396; and 8,928,562; and        U.S. Patent Application Publication Nos. 2003/0102858;        2005/0253777; 2007/0091418; 2007/0103427; 2008/0024429;        2008/0024482; 2008/0136774; 2008/0291129; 2009/0174651;        2009/0179923; 2009/0195568; 2009/0322721; 2010/0220121;        2010/0265561; 2011/0193840; 2011/0193841; 2011/0199671;        2011/0285754; 2013/0063333; 2013/0194250; 2013/0321278;        2014/0009817; 2014/0085350; 2014/0240373; 2014/0253425;        2014/0292830; 2014/0333685; 2015/0070744; 2015/0109283;        2015/0213765; 2015/0221257; and 2015/0262255;    -   (g) Applications of displays; see for example U.S. Pat. Nos.        6,118,426; 6,473,072; 6,704,133; 6,710,540; 6,738,050;        6,825,829; 7,030,854; 7,119,759; 7,312,784; and 8,009,348;        7,705,824; 8,064,962; and 8,553,012; and U.S. Patent Application        Publication Nos. 2002/0090980; 2004/0119681; and 2007/0285385;        and International Application Publication No. WO 00/36560; and    -   (h) Non-electrophoretic displays, as described in U.S. Pat. Nos.        6,241,921; 6,950,220; 7,420,549 8,319,759; and 8,994,705 and        U.S. Patent Application Publication No. 2012/0293858.

Many of the aforementioned patents and applications recognize that thewalls surrounding the discrete microcapsules in an encapsulatedelectrophoretic medium could be replaced by a continuous phase, thusproducing a so-called polymer-dispersed electrophoretic display in whichthe electrophoretic medium comprises a plurality of discrete droplets ofan electrophoretic fluid and a continuous phase of a polymeric material,and that the discrete droplets of electrophoretic fluid within such apolymer-dispersed electrophoretic display may be regarded as capsules ormicrocapsules even though no discrete capsule membrane is associatedwith each individual droplet; see for example, the aforementioned2002/0131147. Accordingly, for purposes of the present application, suchpolymer-dispersed electrophoretic media are regarded as sub-species ofencapsulated electrophoretic media.

An encapsulated electrophoretic display typically does not suffer fromthe clustering and settling failure mode of traditional electrophoreticdevices and provides further advantages, such as the ability to print orcoat the display on a wide variety of flexible and rigid substrates.(Use of the word “printing” is intended to include all forms of printingand coating, including, but without limitation: pre-metered coatingssuch as patch die coating, slot or extrusion coating, slide or cascadecoating, curtain coating; roll coating such as knife over roll coating,forward and reverse roll coating; gravure coating; dip coating; spraycoating; meniscus coating; spin coating; brush coating; air knifecoating; silk screen printing processes; electrostatic printingprocesses; thermal printing processes; inkjet printing processes; andother similar techniques.) Thus, the resulting display can be flexible.Further, because the display medium can be printed (using a variety ofmethods), the display itself can be made inexpensively.

A related type of electrophoretic display is a so-called “microcellelectrophoretic display”. In a microcell electrophoretic display, thecharged particles and the suspending fluid are not encapsulated withinmicrocapsules but instead are retained within a plurality of cavitiesformed within a carrier medium, typically a polymeric film. See, forexample, International Application Publication No. WO 02/01281, andpublished U.S. Application No. 2002/0075556, both assigned to SipixImaging, Inc.

The aforementioned types of electro-optic displays are bistable and aretypically used in a reflective mode, although as described in certain ofthe aforementioned patents and applications, such displays may beoperated in a “shutter mode” in which the electro-optic medium is usedto modulate the transmission of light, so that the display operates in atransmissive mode. Liquid crystals, including polymer-dispersed liquidcrystals, are, of course, also electro-optic media, but are typicallynot bistable and operate in a transmissive mode. Certain embodiments ofthe invention described below are confined to use with reflectivedisplays, while others may be used with both reflective and transmissivedisplays, including conventional liquid crystal displays.

Whether a display is reflective or transmissive, and whether or not theelectro-optic medium used is bistable, to obtain a high-resolutiondisplay, individual pixels of a display must be addressable withoutinterference from adjacent pixels. One way to achieve this objective isto provide an array of non-linear elements, such as transistors ordiodes, with at least one non-linear element associated with each pixel,to produce an “active matrix” display. An addressing or pixel electrode,which addresses one pixel, is connected to an appropriate voltage sourcethrough the associated non-linear element. Typically, when thenon-linear element is a transistor, the pixel electrode is connected tothe drain of the transistor, and this arrangement will be assumed in thefollowing description, although it is essentially arbitrary and thepixel electrode could be connected to the source of the transistor.Conventionally, in high-resolution arrays, the pixels are arranged in atwo-dimensional array of rows and columns, such that any specific pixelis uniquely defined by the intersection of one specified row and onespecified column. The sources of all the transistors in each column areconnected to a single column electrode, while the gates of all thetransistors in each row are connected to a single row electrode; againthe assignment of sources to rows and gates to columns is conventionalbut essentially arbitrary, and could be reversed if desired. The rowelectrodes are connected to a row driver, which essentially ensures thatat any given moment only one row is selected, i.e., that there isapplied to the selected row electrode a voltage such as to ensure thatall the transistors in the selected row are conductive, while there isapplied to all other rows a voltage such as to ensure that all thetransistors in these non-selected rows remain non-conductive. The columnelectrodes are connected to column drivers, which place upon the variouscolumn electrodes voltages selected to drive the pixels in the selectedrow to their desired optical states. (The aforementioned voltages arerelative to a common front electrode which is conventionally provided onthe opposed side of the electro-optic medium from the non-linear arrayand extends across the whole display.) After a pre-selected intervalknown as the “line address time” the selected row is deselected, thenext row is selected, and the voltages on the column drivers are changedto that the next line of the display is written. This process isrepeated so that the entire display is written in a row-by-row manner.

Processes for manufacturing active matrix displays are well established.Thin-film transistors, for example, can be fabricated using variousdeposition and photolithography techniques. A transistor includes a gateelectrode, an insulating dielectric layer, a semiconductor layer andsource and drain electrodes. Application of a voltage to the gateelectrode provides an electric field across the dielectric layer, whichdramatically increases the source-to-drain conductivity of thesemiconductor layer. This change permits electrical conduction betweenthe source and the drain electrodes. Typically, the gate electrode, thesource electrode, and the drain electrode are patterned. In general, thesemiconductor layer is also patterned in order to minimize strayconduction (i.e., cross-talk) between neighboring circuit elements.

Liquid crystal displays commonly employ amorphous silicon (“a-Si”),thin-film transistors (“TFT's”) as switching devices for display pixels.Such TFT's typically have a bottom-gate configuration. Within one pixel,a thin film capacitor typically holds a charge transferred by theswitching TFT. Electrophoretic displays can use similar TFT's withcapacitors, although the function of the capacitors differs somewhatfrom those in liquid crystal displays; see the aforementioned copendingapplication Ser. No. 09/565,413, now U.S. Pat. No. 7,030,412 andPublications 2002/0106847 and 2002/0060321. Thin film transistors can befabricated to provide high performance. Fabrication processes, however,can result in significant cost.

In TFT addressing arrays, pixel electrodes are charged via the TFT'sduring a line address time. During the line address time, a TFT isswitched to a conducting state by changing an applied gate voltage. Forexample, for an n-type TFT, a gate voltage is switched to a “high” stateto switch the TFT into a conducting state.

Undesirably, the pixel electrode typically exhibits a voltage shift whenthe select line voltage is changed to bring the TFT channel intodepletion. The pixel electrode voltage shift occurs because of thecapacitance between the pixel electrode and the TFT gate electrode. Thevoltage shift can be modeled as:

${\Delta\; V_{p}} = {\frac{C_{gp}}{C_{gp} + C_{p} + C_{s}}\Delta}$

-   -   where C_(gp) is the gate-pixel capacitance, C_(p) the pixel        capacitance, C_(s) the storage capacitance and Δ is the fraction        of the gate voltage shift when the TFT is effectively in        depletion. This voltage shift is often referred to as “gate        feedthrough”.

Gate feedthrough can be compensated by shifting the top plane voltage(the voltage applied to the common front electrode) by an amount ΔV_(p).Complications arise, however, because ΔV_(p) varies from pixel to pixeldue to variations of C_(gp) from pixel to pixel. Thus, voltage biasescan persist even when the top plane is shifted to compensate for theaverage pixel voltage shift. The voltage biases can cause errors in theoptical states of pixels, as well as degrade the electro-optic medium.

Variations in C_(gp) are caused, for example, by misalignment betweenthe two conductive layers used to form the gate and the source-drainlevels of the TFT; variations in the gate dielectric thickness; andvariations in the line etch, i.e., line width errors.

Furthermore, additional voltage shifts may be caused by crosstalkoccurring between a data line supplying driving waveforms to the displaypixel and the pixel electrode. Similar to the voltage shift describedabove, crosstalk between the data line and the pixel electrode can becaused by capacitive coupling between the two even when the displaypixel is not being addressed (e.g., associated pixel TFT in depletion).Such crosstalk can result in voltage shifts that are undesirable becauseit can lead to optical artifacts such as image streaking.

The voltage shift between the data line and the pixel electrode may bereduced by altering the geometrical dimensions of the pixel electrodeand/or the data line. For example, the size of the pixel electrode maybe reduced to enlarge the gap space between the electrode and the dataline. In some other embodiments, the electrical properties of thematerial between the pixel electrode and the data line may be altered toreduce crosstalk. For example, one may increase the thickness of theinsulating thin film between the pixel electrode and its neighboringdata lines to reduce capacitive coupling. However, these methods can beexpensive to implement and in some instances impossible due to designconstraints such as device dimensional limitations. As such, thereexists a need to reduce crosstalk in display pixels that are both easyand inexpensive to implement.

The present invention provides means to reduce crosstalk and voltageshifts in display pixels that can be conveniently applied to presentlyavailable display backplanes.

SUMMARY OF INVENTION

This invention provides a backplane for an electro-optic display, thebackplane may include a data line, a transistor, and a pixel electrodeconnected to the data line via the transistor, where the pixel electrodemay be positioned adjacent to part of the data line so as to create adata line/pixel electrode capacitance. The backplane may further includea shield electrode disposed adjacent to at least part of the data lineso as to reduce the data line/pixel electrode capacitance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A illustrates a top view of a display pixel in accordance with thesubject matter disclosed herein;

FIG. 1B illustrates a cross-sectional view of the display pixelpresented in FIG. 1A in accordance with the subject matter disclosedherein;

FIG. 2A and FIG. 2B illustrate a display pixel with shield electrodes inaccordance with the subject matter presented herein;

FIG. 3 illustrates a cross-sectional view of another embodiment of adisplay pixel in accordance with the subject matter presented herein;and

FIG. 4 illustrates a top view of yet another embodiment of a displaypixel in accordance with the subject matter presented herein.

DETAILED DESCRIPTION

As indicated above, the present invention provides a display backplanefor electro-optic displays where crosstalk between pixel electrodes anddata lines are reduced. Such backplanes may include display pixels wherecrosstalk due to capacitive couplings can be shielded by additionalshield electrodes. In some embodiments, the shield electrodes may bepositioned on the same device layer as the data lines and/or in the gapspaces between the pixel electrodes and the data lines.

It should be appreciated that the backplanes described herein may beextended to an electro-optic display comprising a layer of electro-opticmedium disposed on the backplane and covering the pixel electrode. Suchan electro-optic display may use any of the types of electro-opticmedium previously discussed, for example, the electro-optic medium maybe a liquid crystal, a rotating bichromal member or electrochromicmedium, or an electrophoretic medium, preferably an encapsulatedelectrophoretic medium. In some embodiments, when an electrophoreticmedium is utilized, a plurality of charged particles can move through asuspending fluid under the influence of an electric field. Suchelectrophoretic displays can have attributes of good brightness andcontrast, wide viewing angles, state bistability, and low powerconsumption when compared with liquid crystal displays.

FIG. 1A illustrates a top view of a display pixel 100 using a TFT 120 asmeans for switching. The pixel 100 can include a gate line 102functioning as a source line to the display pixel and configured tosupply switching signals to a pixel electrode 104. A data line 106 maybe electrically coupled to the pixel electrode 104 and the gate line 102for supplying driving signals (e.g., waveforms) to the pixel electrode104. In addition, another data line 108 may be positioned adjacent tothe pixel electrode 104 on an opposite side away from the data line 104for providing driving waveforms to a neighboring pixel electrode (notshown). From the top view illustrated in FIG. 1A, the data lines 106 and108 are separated from the pixel electrode 104 by gap spaces 116 and 118respectfully. Referring now to FIG. 1B, FIG. 1B illustrates across-sectional view of the display pixel 100 presented in FIG. 1A. Asshown, the display pixel 100 may include three or more device layers110, 112, 114. In some embodiments, the pixel electrode 104 may bepositioned on a first device layer 110 and the data lines 106, 108 maybe positioned on a third device layer 114, where the first 110 and third114 device layers are insulated by a second device layer 112. The seconddevice layer 112 may include dielectric materials such assilicon-nitride or other comparable dielectric material such that thefirst and third device layers are electrically insulated from eachother. In operation, for example, when the display pixel 100 is beingaddressed (i.e., pixel TFT 120 in conduction), driving voltage signals(i.e., waveforms) are transferred from the data line 106 to the pixelelectrode 104. However, problems can arise when the display pixel 100 isnot being addressed (i.e., associated pixel TFT in depletion) and yetcapacitive coupling between the data lines 106, 108 and the pixelelectrode 104 is still causing voltage values of the pixel electrode 104to shift. As shown in FIG. 1B, electric fields can be coupled betweenthe data lines 106, 108 and the pixel electrode 104 through the seconddielectric device layer 112.

As described above, the coupling of the electric fields between the datalines 106, 108 and the pixel electrode 104 creates undesirable crosstalkand such crosstalk can lead to unwanted optical transitions. One way toreduce such crosstalk and discussed in more detail below is to positionshield electrodes between the data lines 106, 108 and the pixelelectrode 104.

FIGS. 2A and 2B illustrate another embodiment of a TFT pixel 200 wherecapacitive coupling between data lines 202, 204 and the pixel electrode206 may be reduced by placing one or more shield electrodes 212, 214into the gap spaces 208 and 210.

In this configuration, the shield electrodes 212, 214 may be placed nextto the data lines 202, 204 and tied to a voltage source (e.g., ground),where the shield electrodes 212, 214 can hold substantially constantvoltage values during active-matrix scans. As illustrated in FIGS. 2Aand 2B, the shield electrodes 212, 214 may be positioned in proximity tothe data lines 202, 204, and on the same device level as the data lines202, 204. Furthermore, the shield electrodes 212, 214 can substantiallybe of the same geometric shape, or even mirror images to the data lines202, 204, even though other geometric shapes may be conveniently adoptedso long as a reduction in the crosstalk can be achieved. In thisfashion, the data lines 202, 204 are positioned closer to theneighboring shield electrodes 212, 214 than to the pixel electrode 206,and a larger portion of the electrical field from the data lines 202,204 will instead be coupled to the shield electrodes 212, 214. In someembodiments, this diversion of the electric field may be due to the factthat there is less dielectric material between the data lines 202, 204and the shield electrodes 212, 214, and as such the electric fields haveeasier travel paths from the data lines 202, 204 to the shieldelectrodes 212, 214 than to the pixel electrode 206. Put it another way,the mutual capacitance between the pixel electrode 206 and nearby datalines 202, 204 is reduced by the presence of the shield electrodes 212,214. The result is that, when a data line voltage shifts, a nearby pixelelectrode will experience less voltage change through capacitivecoupling because of the presence of the shield electrodes.

It should be appreciated that the placement and geometrical dimensionsof the shield electrodes may be varied so long as the leakagecapacitance between the pixel electrode and the data lines are reduced.For example, different from what's shown in FIG. 2B, where portions ofthe shield electrodes 212, 214 overlap with or extend underneath thepixel electrode 206, in some embodiments, the shield electrodes may bepositioned entirely in the gap spaces between the pixel electrode andneighboring controlling data lines, such that there is no verticaloverlapping between the pixel electrode and the data lines.

In some embodiments, the shield electrodes may be positioned in adifferent device layer than the data lines. Furthermore, the dimensionsof the shield electrodes may be sufficiently large (e.g., wider than thedata lines) to completely shield the data lines from the pixel electrodein the vertical direction, as illustrated in FIG. 3. FIG. 3 illustratesa cross-sectional view of a display pixel 300 where the shieldelectrodes 302, 304 are positioned on the second device level 306,completely shielding data lines 308, 310 below on the third device level312 from the pixel electrode 314 positioned on the first device layer316.

In yet another embodiment shown in FIG. 4, a display pixel 400 mayinclude additional data lines 402, 404 positioned in parallel to thegate line 406. The additional data lines 402, 404 may be positioned on adifferent device layer than the data lines 408, 410 and may be connectedto the data lines 408, 410 through one or more vias 412, 414. In thisconfiguration, shield electrodes (not shown) can be optionally placedbetween the additional data lines 402, 404 and the pixel electrode 416to reduce crosstalk.

It should be appreciated that even though the shield electrodesdescribed in the previous embodiments may be coupled to a fixed voltage(e.g., ground) during the active-matrix scan to maintain a substantiallyconstant voltage value, in some other embodiments, the shield electrodesmay be configured to possess strong capacitive coupling to othersubstantially fixed-voltage electrodes. In this fashion, the shieldelectrodes will still be able to maintain a sufficiently stable voltageand provide reduction to the crosstalk while not be actively driven byexternal electronics.

From the foregoing, it will be seen that the present invention canprovide a backplane for reducing display pixel voltage shifts. It willbe apparent to those skilled in the art that numerous changes andmodifications can be made to the specific embodiments of the inventiondescribed above without departing from the scope of the invention.Accordingly, the whole of the foregoing description is to be interpretedin an illustrative and not in a limitative sense.

The invention claimed is:
 1. A backplane for an electro-optic displaycomprising: a data line; a transistor; a pixel electrode connected tothe data line via the transistor, the pixel electrode positionedadjacent to part of the data line so as to create a data line/pixelelectrode capacitance; and a shield electrode disposed adjacent to atleast part of the data line so as to reduce the data line/pixelelectrode capacitance.
 2. A backplane according to claim 1, wherein theshield electrode extends substantially parallel to the data line.
 3. Abackplane according to claim 1, wherein the shield electrode hassubstantially the same shape as the data line.
 4. A backplane accordingto claim 1, wherein the shield electrode is wider than the data line. 5.A backplane according to claim 1, wherein the data line and the shieldelectrode are positioned on a same device layer.
 6. A backplaneaccording to claim 1, wherein the data line and the shield electrode arepositioned on different device layers.
 7. A backplane according to claim1, wherein part of the shield electrode extends underneath the pixelelectrode.
 8. An electro-optic display comprising a backplane accordingto claim 1, further comprising an electro-optic medium that is arotating bichrome member or electrochromic medium.
 9. An electro-opticdisplay according to claim 8, wherein the electro-optic medium is anelectrophoretic medium comprising a plurality of charged particles in afluid and capable of moving through the fluid on application of anelectric field to the electro-optic medium.